Canadian Science Advisory Secretariat
Science Response 2016/014
Maritimes Region
STATUS OF CUSK (BROSME BROSME) IN NAFO DIVISIONS
4VWX5Z UNDER THE PRECAUTIONARY APPROACH
FRAMEWORK
Context
Cusk, Brosme brosme, is caught as bycatch in certain directed fisheries. Most landings are in
the groundfish longline fisheries. Commercial catch rates for Cusk have declined since the
1980s. Changes to management measures (e.g., reductions to trip limits, overall caps, and
bycatch percentages) may have contributed to this reduction in catch rates (and landings);
however, it is thought the decline in catch per unit effort (CPUE) is also due to a decline in Cusk
abundance (Harris and Hanke 2010). The extent of the decline in abundance is not known.
In 2003, Cusk was assessed asThreatened by the Committee on the Status of Endangered
Wildlife in Canada (COSEWIC). In response to the 2003 assessment, the Governor in Council
decided in 2013 not to add Cusk to the List of Wildlife Species at Risk set out in Schedule 1 of
the Species at Risk Act (SARA). In November 2012, however, Cusk was reassessed as
Endangered by COSEWIC and is subsequently under re-consideration for listing pursuant to
SARA.
The Industry-DFO Halibut Fixed Station Longline Survey (Halibut Survey) catch per station has
been accepted as a biomass index for Cusk (with the catch at each of 57 stations used in the
index standardized to kilograms/1000 hooks). Reference points have been identified based on
the DFO (2009) policy document “A fishery Decision-making Framework Incorporating the
Precautionary Approach” (PA Framework). The Upper Stock Reference (USR) and Limit
Reference Point (LRP) for Cusk were set at 26.6 kg and 13.3 kg, respectively, in the Halibut
Survey (Harris et al. 2012). The 3-year geometric mean of the biomass index was accepted as
the metric for monitoring Cusk status relative to the USR and LRP.
DFO’s Resource Management Sector asked Science to determine the three-year geometric
mean of the Cusk index from the Halibut Survey relative to the USR and the LRP. The
information will be used by DFO Resource Management as guidance in discussions with
various industry stakeholders on recommendations for management measures.
The current 3-year geometric mean (2013-2015) of the Cusk biomass index remains above the
LRP at 19.0 kg., but is within the cautious zone.
The following Science Response Report results from the Science Response Process of
December 7, 2015, on the 2015 Stock Status Update for 4VWX5 Cusk.
Background
The Halibut Survey, a longline survey that samples an area from the Grand Banks of
Newfoundland and along the Scotian Shelf to Georges Bank, is considered to provide a useful
index of trends in Cusk abundance in Northwest Atlantic Fisheries Organization (NAFO)
Divisions 4VWX5 since 1999. Longline gear is an effective sampling tool for Cusk as
March 2016
Science Response: Stock Status Update of Cusk
(Brosme brosme) in NAFO Divisions 4VWX5Z
Maritimes Region
demonstrated by the commercial fishery; over 90% of landings were made by the longline fleets
(Harris and Hanke 2010).
The Halibut Survey is conducted annually, generally between May 22nd and June 22nd.
Variations in the Halibut Survey fishing protocol include a shift to the use of larger hook size,
larger geographic area that each ‘station’ encompasses, lack of consistency in stations
sampled, and variation in soak time and bait type. These variations are not accounted for in the
Cusk biomass index and could contribute to the high variability or bias the estimates.
Description of the Fishery
In the commercial fishery, Cusk are caught primarily in summer and fall, with very limited
landings in winter. While the fishing year runs from April 1st through to March 30th of the
following year, landings from April–November comprise between 93% and 98% of the fishing
year landings from 2007–2014. Cusk landings have been declining, falling to 200t in 2014, and
reaching only 175t by the end of November in 2015. Cusk landings are currently managed by
bycatch caps and trip limits.
Table 1. Cusk Landings in metric tonnes from 2007 to 2015, the most recent complete fishing season is
2014.
Year
4X5YZ
4VW
Total
2007
2008
2009
2010
2011
2012
2013
2014
2015
963
561
535
439
444
442
341
171
146
55
48
38
29
34
39
39
29
29
1018
609
573
468
477
481
380
200
175
Analysis and Response
The 57 fixed stations from the Halibut Survey that have been sampled in all years since 1999
are used to calculate the survey indices for Cusk (Harris et al. 2012). In 2014, data from Station
159 was excluded due to serious damage to the gear, which resulted in a non-typical catch. The
long-term mean for Station 159 is 13.2kg.
The subset of stations includes some of the preferred habitat for Cusk, such as the deeper
areas along the shelf edge, although only a few of these 57 stations are in the Gulf of Maine, the
area of highest commercial landings. The catches at each station (standardized to
catch(kg)/1000 hooks) were used to calculate a biomass index. When the number of hooks
fished was not recorded, it was assumed that the survey standard of 1000 hooks was fished in
the single set. In some cases, stations were fished by 2 or 3 sets of fewer hooks that sum to
roughly 1000 hooks. In these cases, all of these sets were included in calculating the
standardized catch for the station.
The recent trend in the Halibut Survey (3-year running geometric mean) was used as the
biomass index to determine the status of the Cusk biomass in relation to the reference points.
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Science Response: Stock Status Update of Cusk
(Brosme brosme) in NAFO Divisions 4VWX5Z
Maritimes Region
The biomass index from the Halibut Survey has been at or above the proposed LRP since 2008
(Figure 1). A high level of uncertainty is indicated by the wide confidence interval.
Indicator of Stock Status
The 3-year geometric mean (2013-2015) of the survey index for Cusk is 19.0 kg (Figure 1). The
confidence interval of the individual indices in all years, except 2006, encompasses the LRP.
Figure 1. The green dashed reference line represents the upper stock reference point, USR, the red
dotted reference line represents the limit reference point, LRP, the blue diamonds represent the biomass
index for Cusk in the Halibut Survey, including the 95% confidence interval, and the heavy blue line
represents the three-year geometric mean of the index.
Conclusions
The 3-year geometric mean (2013-2015) of the Halibut Survey biomass index for Cusk remains
above the LRP at 19.0 kg.
Contributors
Donald Clark (Lead)
Jennifer Ford
Gary Melvin
Leslie Nasmith
Lottie Bennett
DFO Maritimes Region, Science
DFO Maritimes Region, Resource Management
DFO Maritimes Region, Science
DFO Maritimes Region, Science
DFO Maritimes Region, Science
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Science Response: Stock Status Update of Cusk
(Brosme brosme) in NAFO Divisions 4VWX5Z
Maritimes Region
Approved by
Alain Vézina
Regional Director of Science
DFO Maritimes Region
Dartmouth, Nova Scotia
Ph. 902-426-3490
Date: January 11, 2016
Sources of Information
DFO. 2009. A Fishery Decision-Making Framework Incorporating the Precautionary Approach.
(Accessed January 8, 2016).
Harris, L.E., and Hanke, A.R. 2010. Assessment of the Status, Threats and Recovery Potential
of Cusk (Brosme brosme). DFO Can. Sci. Advis. Sec. Res. Doc. 2010/004.
Harris, L.E., Somers, G., and Clark, D.S. 2012. Reference Points for Cusk (Brosme brosme) in
NAFO Divisions 4VWX5Z Under the Precautionary Approach Framework. DFO Can. Sci.
Advis. Sec. Res. Doc. 2012/026: iii + 10 p.
This Report is Available from the
Center for Science Advice (CSA)
Maritimes Region
Fisheries and Oceans Canada
Bedford Institute of Oceanography
1 Challenger Drive, PO Box 1006
Dartmouth, Nova Scotia B2Y 4A2
Telephone: 902-426-7070
E-Mail: [email protected]
Internet address: www.dfo-mpo.gc.ca/csas-sccs/
ISSN 1919-3769
© Her Majesty the Queen in Right of Canada, 2016
Correct Citation for this Publication:
DFO. 2016. Status of Cusk (Brosme brosme) in NAFO Divisions 4VWX5Z Under the
Precautionary Approach Framework. DFO Can. Sci. Advis. Sec. Sci. Resp. 2016/014.
Aussi disponible en français :
MPO. 2016. Situation du brosme (Brosme brosme) dans les divisions 4VWX5Z de l'OPANO au
regard du cadre de l'approche de précaution. Secr. can. de consult. sci. du MPO, Rép. des
Sci. 2016/014.
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